Fibrillated matrix active layer for an electrode

Abstract

The present disclosure is directed to an improved fibrillated matrix-type active layer for an electrode of improved strength and durability and capable of operation at high current density with enhanced resistance to mechanical failure, and to a process for producing such improved active layers. The process is characterized by alternately or simultaneously producing two components; combining the components; shear blending (fibrillating) the mixture; drying; chopping to a fine powder form, and rolling into a self-sustaining, coherent shear form. Alternatively, the active layer can be formed by wet deposition of the powder on a filter paper or like medium. The term "matrix" as used herein means that the active carbon particles are present within an unsintered network of carbon black/PTFE (fibrillated) material.

What is claimed is: 
     
       1. A method of preparation of matrix active layer for an electrode comprising intimately mixing carbon black particles having a particle size of from about 50 to about 3000 Angstroms and having a surface area of from about 25 to about 300 square meters per gram, with an aqueous dispersion of fibrillatable polytetrafluoroethylene particles; said mixture containing from 65 to about 75 percent carbon black particles and 25 to 35 percent polytetrafluoroethylene by weight; drying said mixture at temperatures in the range from about 250° to 325° C. from 10 to about 90 minutes; combining the thus dried PTFE/carbon black particulate component with deashed active carbon catalyst particles to form an intimate mix said catalyst particles amounting from between 40 to 80 weight percent of the entire mix; fibrillating said intimate mix and forming said fibrillated mixture into an active layer containing active carbon particles present within a network of carbon black and fibrillated polytetrafluoroethylene. 
     
     
       2. A method as in claim 1 wherein said carbon black is an acetylene black. 
     
     
       3. A method as in claim 1 wherein said active carbon particles contain platinum. 
     
     
       4. A method as in claim 1 wherein said active carbon particles range in size from about 1 to about 30 microns. 
     
     
       5. A method as in claim 1 wherein the total mix contains from about 25 to about 50 weight percent of a pore-forming bulking agent.